Bridge Linear Structure (2D) Data Fields

Bridge Linear Structure (2D) data can be edited on either the Bridge Linear Structure (2D) Grid Window of the Lines Grid or the Bridge Linear Structure (2D) Property Sheet.

Most data can be edited on the grid, but some fields cannot be displayed in the grid format.

To view and edit all bridge linear structure (2D) data, use the Property Sheet.

The following describes all the data which can be used to define a Bridge Linear Structure (2D) object.

Common Data Fields

Fields that are common to the majority of objects can be found in the Common Fields topic.

Bridge Linear Structure (2D) Data

Database Table Name: hw_2d_bridge

Show Columns

Database Names

Size, Type and Units

Defaults and Error Limits

Field Name

Help Text

Database Field

Data Type

Size

Units

Precision

Default

Error Lower Limit

Error Upper Limit

Warning Lower Limit

Warning Upper Limit

ID

ID of the line.

line_id

Text

64

 

0

 

0

0

0

0

Asset ID

For reference only. Designed as a reference to an asset database, but could be used for anything.

asset_id

Text

64

 

0

 

 

 

 

 
Discharge coefficient

Enabled when Flow type is set to Controlled or Orifice.

Where the bridge is fully submerged the behaviour is generally in a manner predicted by the discharge theory for an orifice. A typical overall velocity and contraction coefficient is therefore the default value of 1.0.

 discharge_coeff Double     2 1 0.01      
Secondary discharge coefficient

Enabled when Flow type is set to Controlled.

This applies when the depth of water is less than the opening of the bridge, and weir equations apply.

 secondary_discharge_coeff Double     2   0.01      
Overtopping discharge coefficient

Enabled when Overtopping flow type is set to Controlled.

Applies when the gate is overtopped.

 overgate_discharge_coeff Double     2 1 0.01      
Length

Length of the structure.

 length Single   L 3          
Start length

Determines the location of the bridge along the associated base linear structure.

Bridge starts at length measured from the start of the base linear structure.

 start_length Double   L 3 0.0        
Base Linear Structure (2D) ID

ID of associated Base Linear Structure (2D) object.

 linear_structure_id Text 64   0   0 0 0 0
Invert level

Method of specifying invert level.

Database value

Description

Help Text
Height Height Height of invert (above ground level) is specified in the Height field.
Level Level Level of invert (above datum) is specified in the Level field.
Irregular Irregular The invert level of the structure is specified in the Section data editor
crest_level Text 20   0 Level 0 0 0 0
Height

Enabled if Invert Level of type Height is selected.

Height of the bridge invert from ground level.

For each segment of structure, this is the height above the highest of the ground levels of the two computational elements either side of the structure.

 height Double   Y 3 0.0 0      
Level

Enabled if Invert Level of type Level is selected.

Height above datum of the bridge invert.

 level Double   Z 3 0.0        
Flow type

Method of flow calculation.

All three modes are fully mass and momentum conservative.

Database value

Description

Help Text
Free Fully Free

Flow though the opening of the structure is calculated using the Roe approximate Riemann solver based on the geometry of the opening for both free surface flow and pressurised flow.

Flow is not only controlled by the head difference but also by the momentum of the flow. As the flow calculation is consistent in free and pressurised conditions, the flow shows a smooth profile during transitions and is very stable.
Controlled Fully Controlled

Flow is calculated using standard weir and orifice equations using the coefficients set by the user.

Prone to oscillations as the flow calculation is based only on head differences and is therefore only valid for very slow moving flows.
Orifice Orifice Controlled

Flow under free surface conditions is calculated using the Roe approximate Riemann solver. When flow is pressurised, the calculation is switched to orifice and controlled by the coefficients set by the user.

Prone to oscillations as the flow calculation is based only on head differences and is therefore only valid for very slow moving flows.
flow_type Text 10   0 Free 0 0 0 0
Overtopping flow type

Method of flow calculation for flow overtopping the structure.

Both modes are fully mass and momentum conservative.

Database value

Description

Help Text
Free Fully Free

Flow overtopping the structure is calculated using the Roe approximate Riemann solver.

Flow is not only controlled by the head difference but also by the momentum of the flow.
Controlled Fully Controlled

Flow is calculated using standard weir equations using the coefficients set by the user.

Prone to oscillations as the flow calculation is based only on head differences and is therefore only valid for very slow moving flows.
over_flow_type Text 10   0 Controlled 0 0 0 0
Blockage

Blockage factor between 0 and 1, where 0 represents no blockage and 1 represents fully blocked (no flow can pass through bridge).

See Base Linear Structures (2D) for further information.

 blockage Double     3 0.0 0 1    
Headloss specification

Indicates how the headloss coefficient is to be specified. This can be set to:

  • Uniform - one Headloss coefficient is specified which is applied to both the upstream and downstream elements.
  • Upstream & downstream - separate headloss coefficients, US headloss coefficient and DS headloss coefficient, are specified which are applied to the upstream and downstream elements respectively.

See Base Linear Structures (2D) for further information.

 headloss_spec Text 25   0 Uniform 0 0 0 0
Headloss coefficient type

Indicates the type of headloss coefficient to be used. This can be set to:

  • Fixed - the headloss slope across the structure is scaled by the inverse of the distance between element baricentres. Therefore the resulting headloss across the structure is practically independent of the mesh size.
  • Per unit length - the headloss is calculated per unit length and hence it is mesh dependent.

See Base Linear Structures (2D) for further information.

 headloss_type Text 20   0 Fixed 0 0 0 0
Unit headloss coefficient

Enabled when Headloss specification is either not set or set to Uniform, and Headloss coefficient type is either not set or set to Per unit length.

Head loss coefficient per unit length that applies to the adjacent elements of the line structure.

See Base Linear Structures (2D) for further information.

 headloss_coeff Double   UHC 3 0.0 0      
US unit headloss coefficient

Enabled when Headloss specification is set to Upstream & downstream, and Headloss coefficient type is either not set or set to Per unit length.

Headloss coefficient per unit length that applies to the upstream element of the line structure.

See Base Linear Structures (2D) for further information.

 us_unit_headloss_coeff Double   UHC 3 0.0 0      
DS unit headloss coefficient

Enabled when Headloss specification is set to Upstream & downstream, and Headloss coefficient type is either not set or set to Per unit length.

Headloss coefficient per unit length that applies to the downstream element of the line structure.

See Base Linear Structures (2D) for further information.

 ds_unit_headloss_coeff Double   UHC 3 0.0 0      
Headloss coefficient

Enabled when Headloss specification is either not set or set to Uniform, and Headloss coefficient type is set to Fixed.

Head loss coefficient that applies to the adjacent elements of the line structure.

See Base Linear Structures (2D) for further information.

 headloss_coeff2 Double     3 0.0 0      
US headloss coefficient

Enabled when Headloss specification is set to Upstream & downstream, and Headloss coefficient type is set to Fixed.

Headloss coefficient that applies to the upstream element of the line structure.

See Base Linear Structures (2D) for further information.

 us_headloss_coeff Double     3 0.0 0      
DS headloss coefficient

Enabled when Headloss specification is set to Upstream & downstream, and Headloss coefficient type is set to Fixed.

Headloss coefficient that applies to the downstream element of the line structure.

See Base Linear Structures (2D) for further information.

 ds_headloss_coeff Double     3 0.0 0      
Lateral friction coefficient

Coefficient of energy loss caused by the friction of the flow against the line structure in the tangential direction.

See Base Linear Structures (2D) for further information.

 lateral_friction Double     4 0.0 0      
No reverse flow

Check this option to define the structure as unidirectional - flow is only allowed to flow from the structure's upstream side to its downstream side; no reverse flow is allowed.

If this option is unchecked, the structure is taken to be bidirectional and flow will be allowed in both directions.

 use_direction Boolean     0 0        
Section data

Bridge section data.

Database Table Name: hw_2d_bridge_sec

Position in Data Structure

Field Name

Help Text

Database Field

Data Type

Size

Units

Default

Error Lower Limit

Error Upper Limit

Warning Lower Limit

Warning Upper Limit
1 X Coordinate X coordinate of section vertex X Double   L        

 
2 Y Coordinate Y coordinate of section vertex Y Double   L        

 
3 Invert level

Visible when Invert level is set to Irregular.

Elevation of bridge invert at vertex

 Z Double   Z   -9999    

6000
4 Opening height Height of bridge opening opening Double   L   0    

3000
5 Deck thickness Bridge deck thickness deck_level Double   L   0    

 
sections Array     0          

Bridge Linear Structure (2D)

Lines

Lines Grid

Property Sheets